Ampere demand indicator



March 11, 1941. K. c. MARKLEY 2,234,570

AIPERE DEMAND INDICATOR Filed Nov. 1. 1939 2 Sheets-Sheet 1 /7 V A1 I BI-Mergz, U/y/r" hem/4 March 11,1941.

AIIPERE :DEIAND INDICATOR Filed Nov. 1, 1939 2 sneets-shei 2] AZ/mefl 6.

K. c. MARKLEY 2.23 .570

Wan s.

Patented Mar. 11, 1941 UNITED- STTES AMPERE DEMAND INDICATOR Application November 1, 1939, Serial No. 302,447

4 Claims. (01. 171-95) FFHQE The primary object of the present invention is Fig. 3 is a vertical sectional view on line 3-3 to provide an improved ampere demand indiof Fig. 1; I cator, of such simplicity and ruggedness of 0011- Fig. 4 is a sectional view on line 44 of Fig. 1;

struction that not only may great economies in Fi s a s e e t n il ustrating a modifi- 3 initial cost and installation be effected, but also ion ofthe poin er r n ent of Fig. 5 maintenance costs may be reduced to a mere Fig. 6 is aside view illustrating a further modi-' fraction of the present costs of maintenance. fication of the invention, and

Practically all of the demand measurements Fig. Tien elevation looking toward the ri ht 10 as applied commercially in the measurement of in gg electrical energy by public service companies supe nu e a s s ate Corresponding parts 10 plying electricity to consumers read in terms of throughout the Several figures of th d aw kilowatt or watt demand. The demand finding Referring to the d w d particul rly to mechanisms which have heretofore been em- FigS- o 4, a strip of bimeteil 5,.comprising the ployed have been extremely complicated, are very ambient p ra p n i lem is costly, and involve a very considerable expense rigidly fastened at its er end to a p on 5 in the maintenance and servicing of the same. of the suppo structure e innermost e There is at present a trend t ward th m a of bimetallic strip 5 being fastened to central urement of'lower units of demand, and this will, s a t 1 a d Said S a being leurnaled in fixed of necessity,involve the use of very large numbearings 3 and bers of demand measurement appliances or A projection IQ of shaft 1 carries a hub II and meters. The present invention contemplates the light (1150 s hub and disc being firmly fiXed use of a demand measurement mechanism which upon Shaft p j ion t!- A hub I3 and indiwill indicate the demand in terms of amperes at p t 14 a r tata y unted p n rather than in terms of kil tt or tt shaft projection Ii) so as to be relatively free to Ampere demand measurements makes possible rotate but with a light friction fit. The degree the utilization of much cheaper and more rugged of friction is such that when shaft 1 and disc d vi t those used t present to measure 12 are rotated, pointer M will be carried around watts demand, while at the same time more com- With Said Shaft and disc, but a be deflected to pletely covering the original object sought through a y other position a i e to d s 12 po th demand measurement, namely: the protection of application of an external force- A thermal 30 the company producingand selling energy against jacket [5, com rising an electrical resistance overloading of its lines by any particular cus- Winding l5a and a Tetaining Shell jacket, p tomer without corresponding compensatio vides a mass of such a nature as to develop the The present watts demand devices are of two desired thermal time a general classes, one of them purely mechanical, It 18 not desirable that momentary fiiletuatlehs involving a complexity of gears, clutches, etc., Of the ampere 103d be p d s a maXimU-m and an electric timing motor; the other general reading n h in i r, t pon the conclassification being thermal watt demand meters Q the maximum demand which has e involving the use of bimetallic strips, Bourdon mamtelnee reasonabl? penod of tlme tubes, etc., complicated by the introduction of shotnd be mdlcateq by h mdltmtor' Usually the necessary electrical components (transformg ig fi gfii g g ggg ig i gg g zigr g 3: 2 5 1 5 x 1 3 ?::?g$ maybe such as to reach maximum temperature in fifteen minutes, or any other selected time.

ure thermally the heating effect of current, only, A spiral strip of bimetal n which is in every 45 can be much more 51 mp1y than Wat respect a duplicate of the bimetallic spiral 5, has demand dances above mentlonedits outer end fastened to the inner Wall of jacket Str tur s illust f ep i iples f the IS at l6, and its inner end fastened to shaft I8. inventi0 a e ll s n t e a p y Shaft I8 is journaled in fixed bearings l9 and 20,

" drawingsrin Which! so located that the shafts 1 and I8 will be con- 59 Fig. 1 is a side view of an ampere demand indicentric and parallel. A projection 2! of shaft l8 cator constructed in accordance with the invencarries a hub 22 and pusher dog 23, both firmly tion; fixed to shaft projection 2|, the projecting end Fig. 2 illustrates one of the heat responsive of dog 23 being so located that when shaft is 55 units hereinafter described; is rotated, dog 23 may be brought into contact 55 with one side of pointer I4 and may subsequently rotate pointer I4 relative to disc l2.

A calibrated scale is applied to one side of disc I 2, the indicated values being made to correspond to the quantity being measured, which in this case would be the circuit demand in amperes. Electrical leads 24 connect the resistance wire I within thermal jacket I5 to the source of supply, which may be one side of the current coils of a watthour meter, the secondary of a separate current transformer, or the like.

The operation of the device is as follows:

Assume the device to be at room temperature, with pointer I4 set at the zero point of the scale. Assume also that no current flows in the device, that is, the circuit load is zero; under these circumstances, variations in ambient temperature will cause bimetal coils '5 and I! to wind up or unwind by equal amounts and in the same direction, causing shafts 1 and I8, disc I'2, pointer I4 and dog 23 all to rotate simultaneously and in the same direction, so that there is no relative motion between pointer I4 and disc I2, and pointer I4 remains at the zero of the scale. Consequently, variations in ambient temperature by themselves will cause no change in the indication of the device.

Assume now that the device 'is originally set at zero and then connected to the source of current. The resultant heat developed in the resistance winding of jacket I5 will cause the temperature of the latter to rise, and since jacket I5 effectively surrounds bimetal coil II, the temperature of the latter will also rise, causing shaft I8 to rotate in a clockwise direction, when viewed in the direction of Figs. 2, 3 and 4. The rotation of shaft I8 will then cause pusher dog 23 to engage one side of pointer I4, causing pointer I4 to rotate clockwise and upscale, relative to disc I2, to an indicated value depending upon the degree of heat developed within jacket I5; or more specifically, to an indicated value depending upon the rise in temperature of jacket I5 above ambient temperaturesaid temperature rise being a function of the current flowing in the associated circuit.

For any given value of current in the associated circuit, there willthen be a corresponding definite temperature rise within jacket I5, this rise in temperature approaching a maximum and equilibrium value, provided the current is held at a constant value, said maximum point being reached at the end of a period of time which, in demand meters of this general type, is referred to by those versed in the art as the time interval. In consequence of the temperature rise occurring in jacket I5, for every steady and constant value of current there will be a definite angular rotation of shaft I8, and consequently a corresponding definite point on the calibrated dial to which pointer I4 will be advanced.

Assume, now, that the current to be measured is reduced below its previous value. Inspection of the direction of rotation of the parts shown in the figures will show that shaft I8 will rotate counter-clockwise relative to disc I2 and carry dog 23 in a direction which is downscale toward a lower indicated value. But since dog 23 can only exert a push upon pointer l4 in an upscale direction, any downscale motion of dog 23 merely causes the latter to move away from pointer I4 without influencing the previously determined location of said pointer. That is, an increase in current, if it be of sufiicient magnitude, may further advance pointer I4 upscale, but a decrease in current imparts no motion to the pointer I 4. It follows, therefore, that for any number of successive motions of dog 23' upscale or downscale, corresponding to successive increases or decreases in the magnitude of the current being measured, pointer I4 will indicate only the maximum value of the various upscale motions of dog 23, regardless of the order of their occurrence. It will be seen that this maximum value will be the maximum of all upscale motions of dog 23 which have occurred since the time of previous resetting of the indicating pointer I4. The reading of pointer I4 against the scale will then be the maximum demand in amperes.

In the case of rapid fluctuations in the current to be measured, the temperature rise of jacket I5 will be an integrated average or mean which will correspond to some particular equivalent value. of steady or constant current.

A modification of the device is shown in Fig. 5, in which dog 23 is provided with an extension which is essentially a pointer 25 similar to pointer I4 and which overhangs the latter, both pointers being read against a common scale. The purpose of this arrangement is to enable the observer to read both the prevailing value of ampere demand and also the preceding maximum ampere demand. a

Furthermore, although the field of greatest usefulness of the device is as an indicator of maximum ampere demand, it may readily be applied to the measurement of the demand of any other electricalquantity, such as the line voltage of the associated circuit, provided said electrical quantity can be converted into, the heating of a. single mass. Further, the principles involved may be utilized in the demand measurement of heat, from whatever source derived.

From the foregoing description, it'will be seen that the structure herein shown and described provides very simple and inexpensive means for indicating the maximum ampere demand of an electric circuit since the time of last re-setting of the indicating pointer.

It is proposed to apply this device in addition to or in conjunction with a watthour meter, so as to leave an indication upon the indicator of the maximum ampere demand occurring during the meter-reading or billing'period of a particular consumer of electrical energy. The actuation of the indicating element by thermal means, and the utilization of the heat storage properties of an effectively large mass, prevents the device from responding to instantaneous overloads.

An important feature of' the invention is the manner in which it compensates for the effects of variation in ambient temperature. It will be observed that since the two thermally responsive devices, to wit; the spirals 5 and H, are substantially identical-in construction, one cancels the other in so far as the effect of ambient temperature is concerned, leaving only the temperature developed in jacket I5. finally operative upon the indicator.

Correction for variations of ambient temperature is of importance since otherwise an indicator located adjacent a boiler room, for example,

might indicate a greater demand than another indicator located in a cool cellar even though the ends of bimetallic spirals 31 and 38 affixed there to. The outer end of the spiral .31 carries a laterally extending, rigid pusher 39, which projects through an open portion 40 of the disc and is adapted to thrust against the side of the pointer 32 and move it over the scale in a clockwise direction under conditions presently to be described.

The spiral 38 has its outer end affixed to the thermal jacket 41, which corresponds in construction and purpose to the previously described jacket I5. The two bimetallic spirals 31 and 38 both tend to turn the shaft 35 in the same direction under the influence of variations in ambient temperature.

With the outer end of the spiral 38 secured to the wall of the jacket 4|, it follows that there will be no movement of the pusher 39 under the influence of ambient temperature, because if the variation in temperature is such as to tend to cause spiral 38 to unwind, such action will merely turn the shaft 35 in its bearings to a given extent, and since the spiral 31 will tend to unwind to exactly the same degree under the influence of the variation in ambient temperature, the pusher 39 will not move and will exert no thrust against pointer 32.

However, when spiral 31 no longer tends to change its form under the influence of ambient temperature, it then becomes, in a sense, a fixture with respect to shaft 35, and any additional movement of shaft 35 under the influence of heat delivered by the jacket 4| will be translated into movement of pusher 39, along with the shaft 35,

to actuate the pointer.

Emphasis is placed upon the advantage of utilizing the full torque of two separate and individual elements, such as the shafts I and I8, in effecting movement of the indicating means, rather than to attempt to impose opposing torques upon a single element. By thus using the full torque effect of two identical bimetallic members, much more accurate results can be had than would be the case if opposed torques were imposed upon a single element. In this connection it may be pointed out that bimetallic elements of the character described have a limited range of movement, and as they reach the limit of movement their response to changes in temperature becomes greatly lessened.

It is to be understood that the invention is not limited to the precise construction set forth, but that it includes within its purview such changes as may fairly come within either the terms or the spirit of the appended claims.

Having described my invention, what I claim 1. A device of the character described comprising a pair of aligned shafts disposed end to end, a cylindrical metallic mass comprising means for electrically heating the same and into which one of said shafts extends, a thermally flexed spiral embraced by said mass, connected at its outer end to said mass and at its inner end to the last-named shaft, a pusher upon the inner end of the last-named shaft, a second thermally flexed spiral through which the other of said shafts extends and which is connected at its inner end to said shaft, means for anchoring the outer end of the last-named spiral, a graduated disc upon the last-named shaft, a pointer, movable over the graduations of said disc, with which said pusher has engagement in one direction of its movement only, and means for mounting said pointer frictionally with respect to the disc to adapt it to move with the disc or to be moved with respect to said disc under the influence of said pusher.

2. A device of the character described comprising a pair of aligned shafts disposed end to end, a cylindrical metallic mass comprising means for electrically heating thesame and into which one of said shafts extends, a thermally flexed spiral embraced by said mass, connected at its outer end to said mass and at its inner end to the last-named shaft, a pusher upon the in- .ner end of the last-named shaft, a second thermally flexed spiral through which the other of said shafts extends and which is connected at its inner end to said shaft, means for anchoring the outer end of the last-named spiral, agraduated disc upon the last-named shaft, a pointer, movable over the graduations of said disc, with which said pusher has engagement in one direction of its movement only, means for mounting said pointer frictionally with respect to the disc to adapt it to move with the disc or to be moved with respect to said disc under the influence of said pusher, and a second pointer constituting a part of said pusher and partaking of the movement thereof, the first-named pointer remaining inthe position of maximum registration to which it is moved by the pusher, and the last-named pointer indicating the registration at any given movement, said thermally flexed spirals being of substantially identical expansive capacity for any given degree of heat.

3. An ampere demand indicator including a heated metallic mass comprising a resistance winding and a cylindrical shell for the same, a shaft extending through said mass, a bimetallic spiral, capable of being flexed under the influence of heat, having one of its ends attached to the inner wall of said mass and its other end attached to said shaft, a crank-like pusher upon the end of said shaft, a second shaft aligned with the first but otherwise independent with respect thereto, a second thermally flexed bimetallic spiral having its inner end secured to the lastnamed shaft and having its outer end anchored, a graduated disc fixed upon the last-named shaft, the last-named spiral being of substantially identical expansive capacity as the first-named spiral, a pointer frictionally mounted upon the last-named shaft and co-acting with said disc and against a side of which said pusher thrusts,

the said spirals tending to move the disc and the pusher in the same direction, and the said spirals acting to cancel the effective action of ambient heat with respect to the indication of the pointer upon the disc, leaving such indication to represent only that degree to which the firstnamed spiral is moved under the influence of the heated mass beyond the point to which the disc was moved by the action of the secondnamed spiral. I

4. An ampere demand indicator including a heated metallic mass comprising a. resistance winding and a cylindrical shell for the same, means for connecting said winding to a source of current, the ampere output of which is to be measured, a shaft extending substantially axially through said mass, a bimetallic spiral capable of being flexed under the influence of heat having one of its ends attached to the inner wall of said mass and its other end attached to said shaft, said spiral being subject to the influence of heat from said mass and also to the influence of ambient heat entering through open ends of said cylindrical shell, a crank-like pusher upon the end of said shaft, said pusher comprising a portion extending laterally from said shaft having at its end a portion projecting in the general direction of the length of said shaft, a second shaft aligned with the first shaft but otherwise independent with respect thereto, a second thermally flexed bimetallic spiral having its inner end secured to the last-named shaft and having its outer end anchored and being freely exposed to ambient temperatures, a disc fixed upon that end of the last-named shaft which confronts the end of the first-named shaft, 2. scale upon that face of the disc remote from the heated mass, the two spirals being of substantially identical construction and expansive capacity, a pointer frictionally mounted upon the last-named shaft at that side of the disc nearest the heated mass and having a terminal indicating end projecting over such indication to represent only that degree to which the first-named spiral is moved under the influence of the heated mass beyond the point to which the disc was moved by the action of the second-named spiral.

KENNETH C. MARKLEY. 

